Preparation for repairing cartilage defects or cartilage/bone defects in human or animal joints

ABSTRACT

Repairs of cartilage defects or of cartilage/bone defects in human or animal joints with the help of devices comprising a bone part ( 1 ), a cartilage layer ( 2 ) and a subchondral bone plate ( 4 ) or an imitation of such a plate in the transition region between the cartilage layer ( 2 ) and the bone part ( 1 ) show that after implantation the bone part ( 4 ) is resorbed and is replaced by reparative tissue only after being essentially totally resorbed. In a critical phase of the healing process, a mechanically inferior cyst is located in the place of the implanted bone part ( 1 ). In order to prevent the cartilage layer ( 2 ) from sinking into the cyst space during this critical phase of the healing process it is suggested to design the device ( 10 ) in a manner such that its cartilage layer ( 2 ) after implantation is supported on regions with resorbabilities differing from one another. This is for example realized by a device which has a top part ( 11 ) and a bottom part ( 12 ), wherein the top part ( 11 ) consists essentially of the cartilage layer ( 2 ) and the subchondral bone plate ( 4 ) and the bottom part ( 12 ) corresponds essentially to the bone part ( 1 ) and wherein the top part ( 11 ) parallel to the subchondral bone plate ( 4 ) has a larger diameter than the bottom part ( 12 ). After implantation in a suitable opening or bore ( 20 ), the cartilage layer ( 2 ) and the subchondral bone plate ( 4 ) are supported not only on the bone part ( 1 ) but also on native bone tissue having a loading capacity not changing during the healing process. Therefore, the implanted cartilage layer cannot sink during the healing process.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention lies in the field of medical technology andgenerally relates to a device for repairing cartilage defects and/orcartilage/bone defects in human or animal joints. More specifically, thedevice serves to repair defects in the cartilage layer, which in jointscovers the bone surface, or of defects that concern this articularcartilage layer and also bone tissue lying thereunder.

[0003] 2. Description of Related Art

[0004] Damage to articular cartilage by way of injuries or involutioncaused by aging or disease is particularly common in humans. Very oftensuch damage also takes its toll on the bone tissue lying below thearticular cartilage. The degree of damage to articular cartilage defectsand/or cartilage/bone defects is determined with the help of theOuterbridge scale, with the following categories: superficial fraying(approx. 10% of all cases), cartilage fissure (approx. 28%), fissuredown to the bone (approx. 41%), damage involving cartilage and bone(approx. 19%) and other damage such as osteochondritis dissecans andjoint fracture (approx. 2% of all detected cases).

[0005] Vital cartilage tissue contains living cells by way of whoseactivity the specific intercellular cartilage matrix is built up duringadolescence. However, it contains very little vascularization in thefully grown condition and, therefore, has a very limited regenerationcapability. This means that cartilage defects or cartilage/bone defects,in particular those defects concerning a relatively large cartilagesurface, do not heal by themselves and therefore must be repaired bysurgery (Mankin H J: The response of articular cartilage to mechanicalinjury, Journal of Bone and Joint Surgery (Am) 64A (1982) March: pages460-466).

[0006] For repairing the named defects it is, for example, suggested toimplant devices comprising the tissue to be repaired or a perform ofthis tissue. Such devices are cylindrical and comprise a cartilage layeron one end face. For implantation a pocket-hole shaped opening or boreis produced in the region of the defect to be repaired and the device ispositioned in the bore such that the cartilage layer of the implantfaces towards the outside. The bore, independently of the depth of thedefect, extends into the healthy bone tissue. The device has a somewhatlarger diameter than the bore and the same axial length. Therefore,after implantation there is a radial tension (press fit) between nativetissue and the implanted device by way of which the implant is held inthe bore. The cartilage surface of the implant is flush with thesurrounding native cartilage surface. The devices have, according to thesize of the defect, a diameter of 4 to 10 mm (e.g. 5.4 mm for the deviceand 5.3 mm for the bore) and lengths of approx. 10 to 20 mm.

[0007] For larger defects it is suggested to implant a plurality of suchcylindrical devices in the defect region in a mosaic manner and to fillout the intermediate spaces between the implants with a suitablematerial.

[0008] The cylindrical devices are for example autologous(auto-transplants). For the repair of an articular cartilage defectconcerning a heavily loaded location of a joint, a suitable tissue pieceis harvested, for example, from a less loaded location of the same jointand is transplanted into a bore created at the defect location using ahollow drill (Hangody L et al.: Mosaicplasty for the treatment ofarticular cartilage defects: application in clinical practice.Orthopedics 1998 July, 21(7):751-6).

[0009] The cylindrical devices may also originate from a suitable donor(homologous transplants). Also known are suitable heterologue implantsor xeno-transplants which before implantation are suitably treated, e.g.photo-oxidized (as described in the publication EP-0768332 of SulzerInnotec), for preventing immunereaction after implantation or forminimizing such immuno-reaction (immunological deactivation). Suchimplants are, for example, removed from shoulder joints of slaughteredcattle and have the advantage of being available in much larger numbersthan autologous or homologous transplants and of causing no secondarydefects on harvesting, which secondary defects must be repaired and leadto new difficulties.

[0010] In the publication WO-97/46665 (Sulzer Orthopedics) a suitabledevice is described of which the bone part consists of bone replacementmaterial and the end-face cartilage layer is grown onto it in vitro fromautologous chondrocytes.

[0011] In all mentioned devices being made from natural tissue there isa natural connection or coalescence between the end-face cartilage layerand the bone part and there is an outermost bone region (subchondralbone plate) in which the bone tissue is more compact than in other boneregions. The mentioned, partly artificial implants also show thecoalescence of cartilage layer and bone part and the artificial bonepart is advantageously equipped with a more compact, that is to say lessporous, outer layer which serves the cartilage layer as an underlay.

[0012] An important function of the subchondral bone plate or anartificial imitation thereof is evidently the prevention ofvascularisation of the cartilage layer proceeding from the bone tissue,which would lead to ossification of the cartilage. In addition thesubchondral bone plate having a higher density than the inner bonetissue represents a region of higher mechanical strength.

[0013] With the devices as mentioned above it is attempted to achievethe following targets:

[0014] The bone part of the device is to allow solid anchoring of theimplant by way of a press fit, in a manner such that the implantrequires no further fastening means interfering with healthy cartilageregions.

[0015] The coalescence of cartilage layer and bone part in the device isto give the implant stability so that the cartilage layer cannot bedetached and removed from the defect location, even if the joint is notimmobilized after implantation.

[0016] The cartilage layer of the device is to have a mechanicalstrength and elasticity such that the repair location may be fullyloaded directly after implantation.

[0017] The cartilage layer is to form a zone in which conditionssuitable for the implanted cells or for cells migrating into it afterimplantation prevail, such that the cell can produce or maintain a fullyfunctional cartilage tissue. This is also to be supported by thesubchondral bone plate which separates the cartilage layer from the bonepart and which helps to prevent vascularisation proceeding from the bonepart.

[0018] The bone part is to represent a zone in which conditions suitablefor the implanted cells or for cells migrating into it afterimplantation prevail, such that they can produce or maintain a fullyfunctional bone tissue.

[0019] New trials in which artificially produced defects in joints ofsheep have been repaired with auto-transplants, homo-transplants or withhetero-transplants (from cattle tissue) in the previously mentionedmanner, show that the healing process after implantation does notproceed as expected.

[0020] In particular, it has been shown that the bone part of theimplants is not integrated in the native tissue or replaced gradually bynew reparative tissue, but that the bone part of the implant undergoes atransformation process with essentially three successive phases. In afirst step bone osteoclastic cells (osteoclasts) are stimulated and theimplanted bone starts to be resorbed. This first phase is alreadyclearly visible six to eight weeks after implantation. A hollow space(cyst) then arises in the implant and is filled with connective tissue.This second phase reaches a climax after approximately six weeks. In thethird and last phase bone-forming cells (osteoblasts) are attractedwhich convert the connective tissue to bone. This conversion process isconcluded after about twelve months. Then the newly created bonestructure is so well adapted that the original border between theimplant and the surrounding bone tissue can hardly be perceived anymore.

[0021] Due to the described, three-phase transformation processcomprising a middle phase in which the cartilage layer of the implant isnot carried by the bone part capable to do so but by a mechanicallyinferior cyst, there exists a high risk that the cartilage layer ispressed into this cyst where it can neither fulfill its mechanical norits biological function and from where it cannot be displaced during thefollowing phases of the healing process. This risk significantly reducesthe chances of healing success. Healing with a badly positionedcartilage layer causes negative after-effects.

[0022] It is surprising that the trials show the cyst formation at thelocation of the bone part of an implant in a middle phase of the healingprocess not only for homologous and heterologous implants, but inparticular also for auto-transplants. The initial resorption of theimplanted bone tissue does not therefore appear to be an immuno-reactionin which implanted vital material is recognized as foreign and istherefore resorbed. It would appear that it is rather a reaction toimplanted, dead material. This means that by cutting off the naturalblood supply on harvesting the implant even when harvesting it fromviable tissue and even when it is implanted directly after harvesting,the bone tissue loses its viability. In any case, the bone part of theimplant is resorbed and is rebuilt only after substantially completeresorption.

SUMMARY OF THE INVENTION

[0023] It is an object of the invention to provide a device forrepairing cartilage defects or cartilage/bone defects in human or animaljoints, which device prevents the above described risk of an implantedcartilage layer to sink into the region of the native bone tissue. Thedevice according to the invention allows production and implantation ina manner equally simple as for known devices comprising a bone part anda cartilage layer calescent with the bone part.

[0024] The device according to the invention that serves for repairingcartilage defects or cartilage/bone defects in human or animal joints,is based on the finding that the subchondral bone plate is evidentlypresent essentially unchanged when the bone part is completely or to agreat extent replaced by connective tissue in the middle critical phaseof the above described healing process. This is probably attributed tothe fact that the subchondral bone plate, on account of its higherdensity, is resorbed significantly more slowly than the inner regions ofthe bone part. Since this subchondral bone plate is mechanicallysufficiently stable, sinking of the cartilage layer grown thereon into acyst underneath is prevented when the subchondral bone plate issupported not only by implanted bone material but in addition bymaterial with different resorption properties such that during thecritical healing phase it remains non-displaceable. When the subchondralbone plate of the implant is resorbed after the critical phase, that isto say at a point in time in which the loading capability of the innerimplant region is restored again, this will not greatly influence thehealing process.

[0025] Improved support of the implanted device during the criticalhealing phase can be realized in essentially two ways.

[0026] On the one hand the implant may be formed such that the cartilagelayer and the subchondral bone plate of the device have a larger crosssection than the bone part. Such a device is implanted into a two stagebore such that the subchondral bone plate of the device is not onlysupported on the bone part of the implant but also on healthy bonetissue next to the bore set up for repair.

[0027] On the other hand the bone part of the device may be equippedwith columns having a reduced resorbability. These columns extendaxially through the bone part up to the subchondral bone plate. Theresorbability of the columns relative to the resorbability of the bonepart regions between the columns may be reduced by way of a suitablechemical treatment or by way of producing axial bores in the bone partof the device and filling these with an artificial material moreresistant to resorption.

BRIEF DESCRIPTION OF THE DRAWINGS

[0028] These and further features of the invention will be apparent withreference to the following description and drawings, wherein:

[0029]FIG. 1 shows a known cylindrical device for repairing cartilagedefects or cartilage/bone defects in human or animal joints;

[0030] FIGS. 2 to 4 show tissue sections through cartilage/bone defectsin a sheep's joint being repaired with a device according to FIG. 1, atvarious points in time after the implantation;

[0031]FIG. 5 shows a schema of the repair of a cartilage defect with thehelp of a preferred embodiment of the device according to the invention(section along the axis of the device or the bore);

[0032]FIGS. 6 and 7 show two further exemplary embodiments of the deviceaccording to the invention, in cross section; and,

[0033]FIGS. 8 and 9 show sections through a cartilage defect (FIG. 8)and through a cartilage/bone defect (FIG. 9), both repaired in a mosaicmanner with a plurality of inventive devices according to FIG. 5.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0034]FIG. 1 shows a device as used according to the state of the artfor repairing cartilage defects or cartilage/bone defects in human oranimal joints. The device is cylindrical, advantageously with a circularcross section, and comprises a bone part 1 and cartilage layer 2 grownon one end face onto the bone part 1. The cartilage layer 2 forms acartilage surface 3. Between the bone part 1 and the cartilage layer 2there extends a subchondral bone plate 4. The transitions from the bonepart 1 to the subchondral bone plate 4 and from the subchondral boneplate 4 to the cartilage layer 2 are not visible as lines, as is shownin FIG. 1 in a simplified manner, but they are natural, rathercontinuous transitions.

[0035] As already mentioned a device as shown in FIG. 1, is harvestedfrom advantageously vital tissue using a hollow drill and is implantedif possible immediately after harvesting (auto-transplants andhomo-transplants), or it is removed from joints of slaughtered animals(e.g. from shoulder joints of slaughtered cattle) and beforeimplantation is subjected to a treatment for immunological deactivation.

[0036] FIGS. 2 to 4 illustrate the trials with implants according toFIG. 1 in sheep's joints which have already been discussed further aboveand they further illustrate the risk connected with such implants. Thedrawings show tissue sections through repair locations parallel to theaxis of the implant, which in the enlarged drawings projects from thecartilage surface (top side of the Fig.) about 7 cm into the bonetissue. FIGS. 2 and 3 show implant sites six months after implantationwith cyst-like cavities in the bone tissue. FIG. 2 shows a case in whichthe cartilage layer is still positioned at its original location, inFIG. 3 it has sunk into the cyst space.

[0037] As is evident from FIGS. 2 and 3, in the critical time period inwhich at the location of the implanted bone part there is a cyst-likecavity, the subchondral bone plate of the implant is substantiallyunchanged. This finding is attributed to the higher density of thesubchondral bone plate relative to the inner bone tissue and therefore areduced resorbability. The subchondral bone plate of the implant hasevidently different resorption properties than have inner regions of thebone part.

[0038] The trials were carried out with auto-transplants and withhetero-transplants. For seven treated animals the repair locations wereexamined after six months and in ten cases (five animals) cartilagelayers were found to be displaced into the cyst cavity, in four cases(two animals) the cartilage layers had remained in place. In none of thecases the cartilage layer was lost into the joint space.

[0039] The results of the trials show that evidently adhesion betweenthe cyst and the implanted cartilage layer or the subchondral bone platerespectively is sufficient for preventing removal of the cartilage layerfrom the repair location, but that the loading capability of the cyst isnot sufficient for preventing the cartilage layer from being displacedtowards the inside.

[0040]FIG. 4 shows a similar repair location twelve months afterimplantation. An unevenness in the cartilage surface caused by thesinking-in of the implanted cartilage layer is clearly visible. In theseries of trials repair locations on seven treated animals were examinedafter twelve months and in two cases unevennesses in the cartilagesurface as shown in FIG. 4 were found. In the remaining cases thecartilage surface in the repair region was even.

[0041]FIG. 5 shows a preferred embodiment of the device according to theinvention for repairing cartilage or cartilage/bone defects in human oranimal joints. It shows the device 10, the opening or bore 20 to be setup for implantation of the device, and the device inserted in theopening, the implanted device 30 (section along the axis of the device10 or of the opening 20).

[0042] The device 10 has in the same manner as the device of FIG. 1 abone part 1, and on one end face of this, a cartilage layer 2 forming acartilage surface 3. In the transition region between the bone part 1and the cartilage layer 2 there is a subchondral bone plate 4. Thedevice has a top part 11 with a larger cross section and a bottom part12 with a smaller cross section. The top part 11 comprises essentiallythe cartilage layer 1 and the subchondral bone plate 4, the bottom part12 essentially corresponds to the bone part 1. The bottom part 12 hasadvantageously (but not necessarily) the shape of a circular cylinder orsteep angle truncated circular cone and the top part 11 projects on allsides beyond the bone part 1 and is for example likewise circularlycylindrical.

[0043] Auto-transplants and transplants of living donors haveadvantageously cylindrical top parts since such devices should cause assmall as possible harvesting sites. Devices produced from the tissue ofslaughtered animals (advantageously cattle or pigs) may without causingproblems have head parts with any shape of cartilage surface. This is sodue to the easy availability of the material allowing production ofwastage. But also in this case it is advantageous to form the bottompart in a manner such that the opening to be made for implantation canbe created with a simple tool, for example with a drill.

[0044] A device 10 with circular cross section at least in the footregion is for example manufactured from a suitable cylindrical device inthat the bone part is accordingly machined. This machining may becarried out with a tool in which the cylindrical device is positionedand in which blades are activated to reduce the cross section of thedevice 10 to a predetermined extent at a predetermined or adjustabledistance from the cartilage surface.

[0045] The opening or bore 20 which is to be created in a defect regionfor implanting the device 10 has an outer region 21 adapted to the toppart 11 of the device 10 and having a depth down to the region of thenative subchondral bone plate 4′, and an inner region 22 adapted to thebottom part of the device, whose depth is adapted to the shape of thedefect to be repaired and to the length of the device to be implanted.The dimensions of the device 10 and of the bore 20 are to allow for apress fit in the region of the top part as well as in the region of thebottom part.

[0046] A bore 20 as shown in FIG. 5 is for example created with a toolcomprising a blade with a circular cutting edge and two drills or hollowdrills movable relative to the cutting edge in an axially limitedmanner. The tool is positioned on the defect location and the blade ispressed down to the subchondral bone plate. Then the outer region 21 isdrilled out with the first drill, which may be moved beyond the cuttingedge of the blade by the thickness of the subchondral bone plate, andwhose diameter corresponds essentially to the inner diameter of theblade. Afterwards the inner region 22 is drilled out using the seconddrill, wherein the drilling depth relative to the cutting edge orrelative to the end position of the first drill may be adjusted.

[0047]FIG. 5 shows on the right hand side the implanted device 30, thatis to say the device 10 implanted in the bore 20. The implanted device30 comprises a cartilage surface 3 flush with the native cartilagesurface 3′ and a subchondral bone plate 4 roughly flush with the nativesubchondral bone plate 4′. The subchondral bone plate 4 of the implantis evidently supported on the one hand on the bone part 1 of the implantand on the other hand on native bone tissue directly below the native,subchondral bone plate 4′ or in its region. For achieving a press fitfor the head region 1 of the implant, it is advantageous to dimensionthe outer region 21 of the bore with a depth such that the subchondralbone plate 4 of the implant is not only radially supported on nativecartilage tissue 3′ but also on native bone tissue (subchondral boneplate 4′), as this is shown in FIG. 5.

[0048] For implanting a device in a bore, as shown by FIG. 5, a tool isused. The tool comprises, for example, a sleeve and a plunger axiallymovable in the sleeve. The sleeve has an inner cross section thatcorresponds to the cross section of the top part of the device to beimplanted. The plunger advantageously has a cross section roughly equalto the top part; it is longer than the sleeve and has a channel thatbegins on the end face of the plunger and is connectable to a suctionconduit in the region of the other end of the plunger.

[0049] For implantation, the end face of the plunger with the channelopening is pushed into the sleeve and using the suction force, a deviceto be implanted is drawn into the sleeve. Then the sleeve together withthe plunger and the device suctioned thereon is positioned over theprepared bore and the device is pressed into the bore with the help ofthe plunger and where appropriate using a hammer.

[0050] It has been shown that resorption of the bone part of animplanted device also affects regions of the native bone tissuebordering the implant. For this reason it is recommended to dimensionthe protrusion of the top part to about 1 to 2 mm (e.g., bone part witha diameter of approximately 3 mm, top part with a diameter of 5 to 6mm).

[0051]FIGS. 6 and 7 show two further exemplary embodiments of the deviceaccording to the invention. These are not based on the idea ofsupporting the subchondral bone plate of the device on native bonetissue as is shown in FIG. 5, but rather on the idea of establishing inthe bone part at least one column having a resorbability different fromthe resorbability of the rest of the bone material in the bone part 1such that at the point in time in which the remaining bone tissue of thebone part is resorbed, the columns bear the subchondral bone plate andthe cartilage layer grown onto it and, therefore, prevent the cartilagefrom sinking into the cyst region.

[0052]FIGS. 6 and 7 are cross sections through bone parts 1 of devicesaccording to the invention. These devices are, for example, cylindricaland in the bone part have axially extending columns consisting of amaterial that is resorbed more slowly than the bone material of theregions between the columns. The columns are, for example, arranged onthe surface of the bone part (surface columns 40 in FIG. 6) and areproduced by a suitable treatment of the bone material, or they arelocated in the inside of the bone part (inner columns 41 in FIG. 7) andare produced by creating bores and filling the bores with a suitablematerial. In both cases, the columns extend up to at least thesubchondral bone plate.

[0053] For local reduction of the resorbability of bone material, atreatment with biphosphonate may be used (“Biophosphonates in BoneDisease” Herbert Fleisch, the Parthenon Publishing Group, New York andLondon 1995). As a resorbable material for filling bores for example ahydroxy apatite ceramic material may be used.

[0054]FIGS. 8 and 9 show a cartilage defect (FIG. 8) and acartilage/bone defect (FIG. 9) with dimensions of the type such thatthey cannot be repaired with a single implant. The defects are indicatedwith dot-dashed lines. The repair consists of a mosaic-like arrangementof devices according to the invention, as shown in FIG. 5.

[0055] As mentioned above, it is possible also to use implants accordingto the state of the art (FIG. 1) for such mosaic-like arrangements forrepairing larger defects. The cylindrical devices are implanted as closeas possible next to one another, wherein on the one hand there will begaps in the cartilage layer and on the other hand the regions of nativebone tissue between the bone parts of the implants will be very narrow.It has been shown that the chances of healing of such repairs are betterin edge regions than in middle regions. One may presume that this isdue, on the one hand, to the deficient compactness of the freshlycreated cartilage layer and, on the other hand, to the deficient repairability of the greatly reduced native bone tissue between the implants.

[0056]FIG. 8 shows that the implants 30 with the top parts 11 also in amosaic repair allow supporting of the cartilage layer and thesubchondral bone plate of the implants on native bone tissue 1′ andthereby counteract a sinking of the cartilage layer in a criticalhealing phase. It is also evident that the regions of native bone tissue1′ between the bottom parts 12 of the implants are wider than the casewould be with cylindrical implants. This means that the healing chancesare improved in contrast to the state of the art. It is also evidentthat the cartilage surface may be formed essentially withoutinterruption over the complete defect region if the shape of the topparts is accordingly selected (e.g. square, rectangular, triangular, orhexagonal).

[0057]FIG. 9 shows a cartilage/bone defect (indicated with a dot/dashedline) that has been repaired with a plurality of devices according toFIG. 5. The bottom parts 12 of the implants 30 extend into healthy bonetissue 1′. Locations 50 where bone material is missing or damaged bonematerial has been removed are filled out with a suitable material (forexample tricalcium phosphate or hydraulic bone cement). This material isto be selected such that it is resorbed either before or after thebottom parts 12 of the implants 30 and so that, in the critical phase ofthe healing process in which the bone parts of the implants are resorbedand not yet replaced, it can support the cartilage layers and preventthem from sinking. Advantageously the filling material has a mechanicalstrength sufficient for being drilled straight after being filled intothe defect.

[0058] The additional advantages described for the repair according toFIG. 8 apply also to the repair according to FIG. 9.

1. A device (10) for repairing cartilage defects or cartilage/bonedefects in human or animal joints, said device comprising a bone part(11), a cartilage layer (2) grown onto the bone part (1) and forming acartilage surface (3), and in the transition region between the bonepart (1) and the cartilage layer (2) a subchondral bone plate (4) or animitation of such a bone plate, and said device being implantable intoan opening or a bore (20) set up in the defect region in a manner suchthat the bone part is anchored in the healthy bone tissue and thecartilage surface (3) is flush with a native cartilage surface (3′),characterized in that for supporting the subchondral bone plate (4) andthe cartilage layer (2) of the implanted device on at least twomaterials with differing resorbabilities, the bone part (1) has asmaller cross section than the subchondral bone plate (4) and thecartilage layer (2) or the bone part has column regions (40, 41) whichextend to the subchondral bone plate (4) and have a resorbabilitydifferent from the resorbability of the regions between the columnregions.
 2. A device according to claim 1, characterized in that itcomprises a top part (11) and a bottom part (12), wherein the top part(11) substantially comprises the cartilage layer (2) and the subchondralbone plate (4), and the bottom part (12) substantially corresponds tothe bone part and wherein the subchondral bone plate (4) is larger thana cross section parallel to the subchondral bone plate through thebottom part (12) in a manner such that the subchondral bone plate (4) ofthe implanted device (30) is supported on native bone tissue.
 3. Adevice according to claim 2, characterized in that the top part (11) andthe bottom part (12) are coaxial circular cylinders.
 4. A deviceaccording to claim 2, characterized in that the bottom part (12) is acircular cylinder and that the top part (11) has a square, rectangular,triangular or hexagonal cartilage surface (3).
 5. A device according toclaim 1, characterized in that it comprises column regions (40, 41)extending perpendicular to the subchondral bone plate (4) through thebone part (1) up to the subchondral bone plate (4), wherein the columnregions (40, 41) and regions between the column regions have differentresorbabilities.
 6. A device according to claim 5, characterized in thatit is essentially cylindrical and the cartilage layer (3) is arranged onone of its end faces.
 7. A device according to one of claims 5 or 6,characterized in that the resorption behaviour of the column regions(40) is altered with respect to the resorption behaviour of the regionsbetween the column regions by way of chemical treatment.
 8. A deviceaccording to claim 7, characterized in that the column regions (40)consist of bone tissue treated with biphosphonate.
 9. A device accordingto one of claims 5 or 6, characterized in that the column regions (41)consist of a bone replacement material filled into corresponding axialbores.
 10. A device according to one of claims 1 to 9, characterized inthat it is made of autologous tissue.
 11. A device according to one ofclaims 1 to 9, characterized in that it is made of homologous orheterologous, immunologically deactivated tissue.
 12. A device accordingto claim 11, characterized in that it is made of tissue which isimmunologically deactivated by way of photo-oxidation.
 13. A deviceaccording to one of claims 11 or 12, characterized in that it consistsof tissue removed from slaughtered animals.
 14. A device according toclaim 13, characterized in that it is removed from cattle or pig'sjoints.
 15. A method for repairing cartilage defects or cartilage/bonedefects in human or animal joints using a device (10) according to claim2, comprising the steps of producing in the defect region an opening orbore (20) extending into healthy bone material and implanting the device(10) in the opening or bore, characterized in that the opening (20)comprises an outer region (21) and an inner region (22), wherein thecross section of the outer region (21) is larger than the cross sectionof the inner region (22) and that the opening (20) is adapted to thedevice (10) in a manner such that the device is implantable with a pressfit and that the cartilage surface (3) of the implanted device (30) isflush with the native cartilage surface (3′).
 16. A method according toclaim 15, characterized in that the transition between the outer region(21) and the inner region (22) lies directly below the nativesubchondral bone plate (4′).
 17. A method according to one of the claims15 or 16, characterized in that the opening (20) is produced bydrilling.
 18. A method according to one of claims 15 to 17,characterized in that for repairing larger defects a plurality ofdevices are implanted in a mosaic-like manner, wherein positions foropenings or bores (2) and the shape and size of top parts (11) of thedevices (10) are coordinated to one another in a manner such that acartilage surface (3, 3′) essentially without interruption is achieved.19. A method according to claim 18, characterized in that missing bonematerial between the openings is replaced with a bone replacementmaterial having a resorbability which is different from theresorbability of the bone parts (1) of the devices (10).
 20. A tool forproducing the device according to claim 2, characterized by means forpositioning a cylindrical pre-device and by means for reducing the crosssection of the pre-device in the region of the bone part.
 21. A tool forproducing a two-stage bore for implanting a device according to claim 2,characterized by a blade with a circular cutting edge and two drills orhollow drills with different diameters and being movable relative to thecutting edge in an axially differently limited manner.
 22. A tool forimplanting a device according to one of claims 1 to 14, characterized bya sleeve and a plunger axially movable in the sleeve, wherein the sleevehas an inner cross section coordinated to the largest cross section ofthe implant and wherein the plunger comprises a suction channel whichends on one end face of the plunger and is connectable to a suctionconduit in the region of the other plunger end.